<!DOCTYPE HTML>
<html>

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <title>定时器</title>
  <script type="text/javascript">
    var attime;

    function clock() {
      var time = new Date();
      attime = time.getHours() + ":" + time.getMinutes() + ":" + time.getSeconds();
      document.getElementById("clock").value = attime;
    }
    setInterval(clock, 100)
  </script>
</head>

<body>
  <form>
    <input type="text" id="clock" size="50" />
  </form>
</body>

</html>